Technical Abstract:
Cold-hardening plants at above freezing temperatures significantly contributes to their overall winter hardiness. Little research has been conducted however, on hardening at temperatures below freezing, before freezing injury results. Barley and oats were grown and hardened under controlled conditions and freeze tested after being held at -3 degrees C from one to 7 days. The biggest change, a reduction in LT-50 of 7 degrees C, occurred after the second phase of hardening (2PH) in the winter hardy oat cultivar, Wintok. In addition, after 2PH all 15 fructan isomers of degree of polymerization 3 (DP3) to DP5 in oat were lower while the sugars fructose and sucrose were higher. All carbohydrate changes except that of one DP5 isomer and of fructan DP>6 were correlated with survival of plants after 2PH. Possible mechanisms associated with 2PH will be discussed.